Increasingly stringent statutory regulations relating to permissible pollutant emissions of motor vehicles in which internal combustion engines are disposed make it necessary to minimize the pollutant emissions during operation of the internal combustion engine. This can be accomplished on the one hand by reducing the pollutant emissions that are produced during the combustion of the air/fuel mixture in the respective cylinder. For this purpose a precise metering of fresh air and recirculated exhaust gas is necessary. In particular dynamic operation with increasingly higher degrees of supercharging of internal combustion engines requires good control and regulation in order to reduce emissions during transient operation as well as to realize a convenient torque response.
For petrol as well as for diesel internal combustion engines it is known on the one hand to compress the aspirated air before it flows into the cylinders of the internal combustion engine, and on the other hand to recirculate exhaust gas discharging into an exhaust gas tract of the internal combustion engine after combustion to an external exhaust gas recirculation device and mix it with the fresh gas mass that is to be supplied. In this way nitrous oxide emissions in particular can be reduced as a result of a lower combustion temperature. In order to compress the intake air, use is often made of exhaust gas turbochargers whose drive is formed by means of a turbine which is disposed in the exhaust gas tract of the internal combustion engine and is mechanically coupled to a compressor in the intake tract of the internal combustion engine. Actuators are provided in each case for setting the compressor power output and also the exhaust gas mass that is to be recirculated. An intervention into the respective actuator of the external exhaust gas recirculation system or the exhaust gas turbocharger also has an effect in each case on the behavior of the respective other system, i.e. of the exhaust gas turbocharger or of the exhaust gas recirculation system.
A model-based predictive controller for simultaneously regulating the boost pressure and the EGR rate in a diesel engine is known on the one hand from the article titled “Simultane Regelung von Ladedruck und AGR-Verhalten beim PKW-Diesel-Motor” (“Simultaneous control of boost pressure and EGR behavior in automobile diesel engines”), Motortechnische Zeitschrift (MTZ) 11/2001, pages 956 ff.; also known, on the other hand, is a feedback control structure having controllers for the exhaust gas recirculation system and the exhaust gas turbocharger. The actuating variable of the controller assigned to the exhaust gas turbocharger is a variable turbine geometry setting. The output variable of the exhaust gas recirculation controller is a setting of an exhaust gas recirculation valve. In order to decouple the two control loops it is known from the above-cited technical article to provide decoupling elements whose input variables are in each case the actuating variables of the other controller and whose output variables are then added to the actuating variable of the respective controller.
A dynamic model of an internal combustion engine having an exhaust gas turbocharger and an exhaust gas recirculation system is known from a further technical article titled “Die Regelstrecke eines PKW-Dieselmotors mit Direkteinspritzung im Hinblick auf Ladedruck- und Abgasrückführ-Regelung” (“The controlled system of an automobile diesel engine with direct injection with regard to boost pressure and exhaust gas recirculation control”), MTZ 1999, pages 186 ff.